A common type of Field Effect Transistors (FET) is a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET), which may be fabricated using silicon. As is known to those of ordinary skill in the art, a typical circuit application for a MOSFET device is a synchronously-rectified step-down (buck) DC-DC converter output stage. A DC-DC converter functions to “step-down” a DC voltage. For example, a power supply may provide 12V DC and a component (e.g., processor or other semiconductor device) may require 1V DC. In this situation a DC-DC converter may be interposed between the power supply and component to provide the required voltage. The basic operation of a buck converter is known to those of ordinary skill in the art.
The inductor in a buck converter can discharge current back into the MOSFET device(s) when not supplied with power. Silicon MOSFET devices include an intrinsic body diode that is useful for blocking current surges from an inductor. Unfortunately, body diodes also consume power and increase the size and cost of the devices. Additional diodes may be used to supplement current blocking inherent in the body diode of a MOSFET. Unfortunately additional diodes increase the cost of a circuit. A compound semiconductor FET such as a GaAs FET is generally not used in rectified step-down (buck) DC-DC converter circuits or other circuits that include transient sources such as inductors because a GaAs FET does not include an intrinsic body diode for blocking current surges. While a diode may be included in a compound semiconductor FET during fabrication of the device this is an unattractive alternative due to increased cost, complexity and size. Similarly diodes used in the circuit design increases cost and parts count.